Answer:
[tex]\frac{9}{8}[/tex] feet per hour fast is Kelly's knitting speed
Step-by-step explanation:
Unit rate defined as the rates are expressed as a quantity 1 such as 4 meter per seconds or 4 miles per hour.
As per the statement:
Kelly is knitting a scarf for her brother. it took her 1/3 hour to knit 3/8 foot of the scarf.
She took /3 hour to knit 3/8 foot of the scarf.
Then by definition of unit rate we have;
[tex]\text{Unit rate per hour} = \frac{\frac{3}{8} }{\frac{1}{3} } =\frac{3}{8} \cdot 3 = \frac{9}{8}[/tex] feet
Therefore, [tex]\frac{9}{8}[/tex] feet per hour fast is Kelly's knitting speed.